The associations of TAC1 gene polymorphisms with major depressive disorder

Backgrounds: Substance P, which is encoded by tachykinin precursor 1 gene (TAC1), has been implicated in the regulation of stress responses and the pathogenesis of major depressive disorder (MDD). Methods: We evaluated the association of 10 SNPs on TAC1 with MDD susceptibility in 111 patients with MDD and 79 control subjects, and with 17-item Hamilton depression rating scale (HAMD17) score in MDD patients. Results: In all subjects, haplotype (ht) 2 homozygous individuals showed higher plasma substance P levels than subjects carrying one or no copy of ht2. The minor allele frequency of rs1397202 was higher in patients with MDD than that in control subjects. Patients homozygous for the minor allele of rs1397202 showed significantly lower HAMD17 scores than patients carrying the common allele. Conclusion: Our results suggest a possible involvement of genetic variants of TAC1 with the plasma level of substance P and symptom severity of MDD.